This article classifies the major approaches to the assessment of the process and outcomes of medical care. The apparent need to safeguard and enhance the quality of care has led to the institution of mechanisms that subject care to constant review so that deficiencies may be found and corrected. The article reviews the developments that led to the involvement of the federal government in this activity through its sponsorship of professional standards review organizations (PSRO's). The major features of the PSRO's are described and their possible effects discussed. It is too early to say how the PSRO's will fare, but should they fail to accomplish their objectives the pressure for more radical solutions will be difficult to resist.